In addition to the wonderful animal life here, Tanzania is also famous for being the cradle of mankind. In the 1930's when it was still a colony, a German entomologist wandered through the Oldupai Gorge looking for butterflies after the rainy season. Running water had cut through six major layers of rock to the lava bed and revealed a skull that could have been a monkey or could have been a man. Louis and Mary Leakey returned to the gorge and excavated further, finding a definitive skull in 1951 that was our earliest ancestor 1.5 million...